Products for processing and sterilizing drinking water consisting of mixtures of silver sulfate or silver nitrate and sodium chloride are already on the retail market. These products are added to the drinking water in small quantities which are sufficient to keep the water permanently sterilized and fresh by virtue of the bactericidal action of the silver compounds. However, the disadvantage of these known agents is that they must be stored in the dark as they are not light-resistant. When products of this kind are exposed to light, black dots become apparent in them after only a short period of exposure owing to the reduction of the silver compounds to form metallic silver.